This invention relates generally to the fabrication of liquid crystal displays (LCDs) and, more particularly, to a system and method of peeling a sheet of polarizer film from an LCD display in a repair procedure.
Technological advances in design and fabrication have permitted LCDs to replace cathode ray tubes (CRT). The size, weight, and power consumption of the CRT have limited its use in both portable and large screen electronic products. The pixel resolution of the LCD continues to improve, making both large and small screen displays realizable. As LCD costs continue to decrease, it has increasingly become an economical competitor to the CRT.
LCDs operate by controlling the polarity of a light through a transmissive dual phase (liquid/crystal) medium. The LCD allows light of substantially only one polarity to pass through the display, the specific polarity varies for different systems. The liquid crystal molecules on one side of a display are aligned in a first direction, while the liquid crystal molecules on the other side of the screen are typically aligned in a perpendicular direction. Light must, therefore, undergo a 90 degree rotation in polarity as it passes through the display. Sheets of polarizing film are applied to the outside surface of the displays with a polarization matching the initial liquid crystal alignment. The LCD is designed to "twist" light 90 degrees, to pass through the display in one state, and to rotate the light an additional 90 degrees in a second state, so that light is absorbed by the polarizer. In this manner, the intensity of every pixel of light of the LCD is controlled.
A typical electronics device using an LCD undergoes many stages of fabrication and testing before the product is complete. It is not unusual for the pliable thin sheets of polarizer film covering the hard glass surfaces of the LCD to become damaged or scratched in production. Then, the damaged polarizer film must be removed and replaced with another film. Further, in use of the electronic product the polarizer film, or LCD may become damaged so that the polarizer film must be removed in the repair process.
Figs. 1a and 1b illustrate a tool 10 to remove a sheet of polarizer film 12 from an LCD 14 (prior art). An operator begins the process by pulling a corner of the film from the LCD, and inserting the corner into a slot 16 in tool 10 (Fig. 1b). The operator then rotates tool 10 to separate polarizer film 12 from LCD 14. Unfortunately, tool 10 provides no alignment between tool 10 and LCD 14, so that film 12 is pulled unevenly, or tool 10 directly touches areas of LCD 14. LCD 14 is often damaged as the unequal pressures applied during the removal of film 12 permanently disturb the alignment of liquid crystal molecules, or displace the cell gap between the two sheets of glass. This problem is exacerbated by the necessity of the operator to start and stop the film peeling process to re-grip the handle of tool 10 and to realign tool 10 with LCD 14.
It is well known to fabricate LCD 14 with discrete electronic components 18 placed around the periphery. Discrete components 18 are typically needed for functions requiring the high electron mobility of single crystal transistor devices. As is well known, LCDs are typically fabricated with amorphous or polycrystalline silicon that form transistors having poor electron mobility. Because of the high profile of discrete components 18, relative to the flat surface of LCD 14, discrete components 18 are often damaged by tool 10 in the process of removing film 12.
It would be advantageous if a tool could be developed to properly align an LCD with respect to the removal tool in the process of pulling a polarizer film from an LCD.
It would be advantageous if a process could be developed for protecting the surface of the LCD, and any peripherally mounted parts, when a polarizer film is removed from an LCD.
It would be advantageous if a film removal system could be developed to minimize or eliminate any direct pressure on the surface of the LCD in the process of peeling a polarizer film from the LCD surface.
It would be advantageous if a tool could be developed to peel the polarizer film from an LCD in one continuous motion to minimize the cell gap displacement between the two plates of LCD glass.
Accordingly, a system for peeling a sheet of polarizer film adhered to a liquid crystal display (LCD) panel, is provided. The system comprises a take-up roller having a rotational axis and a surface to accept polarizer film as it is peeled. The rotation of the take-up roller peels the polarizer from the LCD and advances the position of the LCD panel along a first plane tangent to the take-up roller surface. The system also comprises at least one alignment roller having a rotational axis parallel to the rotational axis of the take-up roller, and including a cylindrical non-compressible core with a surface. The first alignment roller also includes a cushioned tube having an inside surface adjoining the core and an outside surface. The first alignment roller aligns the LCD in the first plane, which is tangent to the compressed outside surface of the cushioned tube when the polarizer film is engaged with the take-up roller. In this manner, alignment in the first plane helps distribute forces on the LCD more equally as the polarizer is peeled.
The preferred embodiment of the invention further comprises a second alignment roller having a rotational axis parallel to the rotational axis of the take-up roller, and including a cylindrical non-compressible core with a surface. The second alignment roller includes a cushioned tube having an inside surface adjoining the core and an outside surface. The second alignment roller aligns the LCD in the first plane, which is tangent to the compressed outside surface of the second alignment roller cushioned tube when the polarizer film is engaged with the take-up roller. The second alignment roller acts to further distribute the forces on the LCD, and to control the alignment of the LCD in the first plane after it has passed the take-up roller and been stripped of polarizer. The first alignment roller acts to align the LCD in the first plane as it reaches the take-up roller.
The system also includes a slot along the surface of the take-up roller to accept a corner of the polarizer film, initializing the peeling process. A crank is attached to the take-up roller so that the rotational axis of the take-up roller is aligned with the rotational axis of the crank. The crank permits the operator to apply constant rotation to the take-up roller so that the LCD is not exposed to "jerky" start-and-stop motions which stress the LCD glass and liquid crystal medium by displacing the cell gap between the LCD glass sheets.
Typically, the first and second alignment roller cushioned tubes are polyethylene having an uncompressed thickness, between the inside and outside surfaces, of approximately 0.25 inches, to accommodate any peripheral parts along the edge of the LCD panel. Under compression, when the LCD is aligned in the first plane, the polyethylene compresses approximately 0.05 inches so that the shortest distance between the first plane, as it intersects either the first or second alignment roller, and the alignment roller core surface is in the range between 0.190 and 0.210 inches. In this manner, the cushioned tubes are compressed hard enough to distribute the forces along the LCD surface, but compressed light enough to accommodate the profile of peripherally mounted parts.
In a system including a take-up roller and at least one alignment roller having a rotational axis parallel to the rotational axis of the take-up roller, and including a cylindrical non-compressible core with a surface, and a cushioned tube having an inside surface adjoining the core and an outside surface, a method of peeling polarizer film adhered to an LCD panel, is provided. The method comprises the steps of:
a) engaging the polarizer film with the take-up roller; PA1 b) aligning the LCD on a first plane tangent to the take-up roller and to the compressed outside surface of the first alignment roller cushioned tube; PA1 c) rotating the take-up roller; and PA1 d) simultaneously wrapping polarizer film peeled from the LCD around the take-up roller, and pulling the LCD along the first plane past the take-up roller, whereby the alignment roller helps distribute the forces on the LCD as the polarizer is peeled.